Jujutsu Kaisen is a dark fantasy shonen series where negative human emotions can create curses, supernatural spirits that can cause serious harm. Fortunately, jujutsu sorcerers are on hand to fight off curses with curse energy of their own, and protagonist Yuji Itadori dove headfirst into this world when he ate a finger of Sukuna (the first of several).
Source:https://www.cbr.com/jujutsu-kaisen-yuji-itadori-best-friends/